Released in 1940, Spare a Copper was the latest success in a long line of extremely lucrative Formby comedies. By now, the comedian was the highest paid entertainer in Britain and, according to the Motion Picture Herald, the country's top cinema box-office attraction. However, though entertaining, well performed and enthusiastically received by his devoted audiences, Spare A Copper represents a slight downturn in the quality of the Formby productions, which, with the exception of the excellent Turned Out Nice Again (d. Marcel Varnel, 1941), Formby's final film for ATP, went into a decline that became gradually evident in the comedian's later work for Columbia Pictures.

Though topical in its narrative preoccupation with the war effort, Spare a Copper's convoluted plot, involving shipyard saboteurs and stolen propeller blades, is unwieldy and overly complex. Potential for character comedy is squandered; instead there is an over abundance of obviously back-projected slapstick tomfoolery, unpretentiously entertaining in its own straightforward way, but implausible and overdone.

Formby was always a little self-conscious about the inclusion of songs in his comedies. "I always felt they came to a stop whenever I had to play the uke," he recounted. "When that was finished we could get on with t'fun." However, his films are invariably improved by their inclusion; never more so than in the case of Spare a Copper, where the songs provide an essential counterpoint to the gormless Formby persona, fleshing out a character that the sketchy script does not. Of particular note in this regard is 'I'm Shy', a romantic number with unusual, slightly eerie, but highly effective organ accompaniment.

No doubt utilising the experience he gained from working on Spare a Copper, director John Paddy Carstairs would later go on to direct a massively popular series of films starring Formby's logical comic descendent, Norman Wisdom.